APA (7th ed.) Citation

Hey David. (2006). The 9 dimensions of the soul: [essence and the enneagram]. O Books.

Chicago Style (17th ed.) Citation

Hey David. The 9 Dimensions of the Soul: [essence and the Enneagram]. Winchester: O Books, 2006.

MLA (8th ed.) Citation

Hey David. The 9 Dimensions of the Soul: [essence and the Enneagram]. O Books, 2006.

Warning: These citations may not always be 100% accurate.